1. Field of the Invention
The present invention relates to a composition, and method of manufacture thereof, for transdermal delivery of pain relieving substances directly to afflicted areas of the body.
2. Description of the Prior Art
Debilitating diseases such as rheumatoid arthritis and osteoarthritis afflict 37 million people in the United States. The Arthritis Foundation estimates that 10% of the population of the world and 25% of the population of the United States suffer from arthritis to some degree. Fourteen million work days are lost each year in the United States by arthritis victims.
Arthritis is a disease symptomized by painful joints stemming from inflammation in the joint region. Arthritis attacks young, middle-aged and old people alike. Due to the severity of this disease a number of nonsteroidal anti-inflammatory drugs (NSAIDs) have been developed for the treatment of generalized muscle and joint aches, and for the pain of arthritis. aspirin (acetylsalicylic acid), ibuprofen (2(-isobutylphenyl) propionic acid), methotrexate (N-[4-[(2,4 diamino-6-pteridinyl)-methyl]methylamino]benzoyl)-L-glutamic acid), capsaicin (8 methyl-vanillyl-nonenamide) and diphenhydramine (2-(diphenyl-methoxy)-N,N-dimethylethylamine hydrochloride) are only a few of the medicaments that are available in prescription and over the counter formulations for the alleviation of pain.
Unfortunately these medicaments have major side effects caused by the systemic (typically by oral ingestion) administration. For instance, an example of the side effects of ibuprofen when administered in recommended therapeutic doses (e.g. 1000-2400 mg.qd) are esophagitis, nausea, epigastric pain, heartburn, diarrhea, vomiting, abdominal cramps, bloating and flatulence, dizziness, headache, nervousness, dermatologic rash, blurred or diminished vision, edema, fluid retention, elevated blood pressure, palpitations, gastric or duodenal ulcer, hepatitis, jaundice, gastrointestinal hemorrhage, melena, gastritis, abnormal liver function, kidney damage, kidney failure, acute renal failure, and congestive heart failure in patients with marginal cardial function. The Physicians Desk Reference (PDR) lists these possible side effects and many more when taking ibuprofen, for example, systemically for the relief of pain.
In addition to these side effects when ibuprofen is administered systemically, only a small amount of the ingested drug is delivered to the specific pain area. An example would be if pain and inflammation exists in the front of the knee, and 1000 mg. of ibuprofen is taken orally. Only a small fraction of the ibuprofen actually reaches the pain area. Also, there is a considerable time lapse between injection and the relief of the pain. Clinical studies have shown that following the ingestion of ibuprofen, as much as 79% of the ingested dose is filtered out by the kidneys and is recovered in the urine within 24 hours. This leaves an average of only 21% of the recommended dose of ibuprofen available for systemic distribution throughout the body. Also, the amount of time for relief of pain with systemic application of the drug is between 45 minutes and 120 minutes.